Zack Snyder's Justice league is what happens when a director is given the keys to the sweet shop. The ensuing scene is a operatic epic of gastronomic gorging on everything - more! more! more! There can never be enough candies, caramels and chocolates, white mice, Jelly beans, cola bottles, those 2 metre long marshmallows you are fed it all until you sit feeling very bloated crashing from a sugar high with chocolate smeared around your grinning face...
By contrast the 2017 Whedon cut was the child who visited the same sweet shop with a too small allowance and only 2 minutes to decide what you really want... You come away with a bag of treats but ultimately unsated and lamenting the fact you didn't have enough for the jelly babies.
Snyder's movie has significantly longer to do more. Characters are given more back-story, we have time to reflect upon events instead of bounding from too short scene to too short scene. There are opportunities to set the tone with more imagery and music. The story and the director can take his time.
That doesn't pay off in every instance, though. That longer runtime certainly improves things in one way - but some of the changes Whedon made to get his cut to a shorter run-time are simply better written.
The most obvious example of a major change is the expanded Cyborg arc. Snyder takes a long time to establish the character's back story, his powers and abilities and his strained relationship with his father. The problem is that its just not well done at all. The dialogue is entirely expository and the choice of visuals used to demonstrate Cyborg's powers are basically achieved with poor CGI. Whedon managed the same character work in 2 minutes of fantastic dialogue - but its ultimately too short and leaves you wanting much more.
Some of Whedon's jokes never really landed in the theatrical cut and these are thankfully absent in Snyder's version. Where Whedon's best work on the movie was most evident was where he was forced to get to the point quicker by a studio mandated shorter runtime. The longer Snyder-cut unfortunately loses some of Whedon's better additions in favour of a significantly slower burn. Its 2 hours into Snyder's cut before we get Batman in the batsuit... in Whedon's cut its in the first 10 minutes which is more satisfying.
Some scenes in Snyder's version benefit from being given more time to breathe - others very much don't. There is a lot of Amazonian mourning and a nonsensical icelandic wailing song at the end of the first Aquaman scene which add nothing - but there is also time taken to establish the mood of scenes that Whedon had to rush through. The longer fight scenes are also better composed in Snyder's version - although his over-use of slow motion and bullet-time in these sequences borders on the absurd.
Snyder also throws characters into his cut that have no reason to be there. Martian manhunter adds nothing as does the character of Iris West - basically there for the Flash to oggle over for an uncomfortable 30 seconds that makes the character feel somewhat pervy.
But Snyder also gets to add in 2 extra villains that serve the narrative of the movie far better and make for a more compelling primary antagonist and much higher stakes.
Somewhere in this 4 hour slog is an excellent 3 hour movie but as it stands it creates as many issues as it solves.